XQuery Questions and Answers for Viva

Answer-1: XQuery is a query language designed to query and manipulate XML data. It allows extraction and transformation of data from XML documents, databases, and web services.

Answer-2: The primary purpose of XQuery is to query XML data, retrieve specific information, and transform XML documents into other formats such as HTML, plain text, or XML.

Answer-3: XQuery is a full query language that builds upon XPath for querying XML data. XPath is a subset of XQuery, primarily used for navigating XML documents.

Answer-4: FLWOR stands for "For, Let, Where, Order by, Return" and is used in XQuery to iterate over XML data, filter, sort, and return results.

Answer-5: Variables in XQuery are declared using the let or for keywords. Example: let $x := "Hello"

Answer-6: XQuery returns sequences of items, which can be XML elements, attributes, strings, numbers, or other data types.

Answer-7: Use the where clause to filter data in a FLWOR expression. Example: for $book in /books/book where $book/price > 20 return $book/title.

Answer-8: Use the order by clause to sort data. Example: for $book in /books/book order by $book/price return $book/title.

Answer-9: Use the path syntax: /elementName. Example: /books/book.

Answer-10: Yes, XQuery can handle JSON data using the XQuery 3.1 standard, which provides JSON support.

Answer-11: Use the for and where clauses to define the join condition and combine data from both documents.

Answer-12: A sequence is an ordered collection of items, which can be nodes or atomic values. Example: (1, 2, "abc").

Answer-13: The distinct-values() function removes duplicate values from a sequence.

Answer-14: Use (: and :) for comments. Example: (: This is a comment :).

Answer-15: XQuery supports XML Schema types, including string, integer, boolean, date, decimal, and more.

Answer-16: The doc() function loads an external XML document for querying. Example: doc("books.xml").

Answer-17: Use the @ symbol. Example: /books/book/@id.

Answer-18: The fn:concat() function concatenates multiple strings. Example: concat("Hello, ", "World!").

Answer-19: The count() function counts the number of items in a sequence. Example: count(/books/book).

Answer-20: Use the declare namespace keyword. Example: declare namespace ns = "http://example.com";.

Answer-21: The fn:substring() function extracts a substring from a string. Example: substring("Hello, World!", 1, 5) returns "Hello".

Answer-22: The fn:contains() function checks if a string contains a specified substring. Example: contains("Hello, World!", "World").

Answer-23: No, XQuery is a read-only query language. For updates, XQuery Update Facility (XQUF) is used.

Answer-24: The empty() function checks if a sequence is empty. Example: empty(/books/book) returns true if no elements exist.

Answer-25: The fn:starts-with() function checks if a string starts with a specified prefix. Example: starts-with("XQuery", "X").

Answer-26: Use the if-then-else construct. Example: if ($price > 20) then "Expensive" else "Affordable".

Answer-27: The for clause iterates over a sequence. Example: for $book in /books/book return $book/title.

Answer-28: The fn:ends-with() function checks if a string ends with a specified substring. Example: ends-with("Hello", "o").

Answer-29: Use angle brackets to create new elements. Example: Content.

Answer-30: doc() retrieves a single XML document, while collection() retrieves a collection of XML documents.

Answer-31: The fn:string-join() function concatenates a sequence of strings with a delimiter. Example: string-join(("a", "b", "c"), ",").

Answer-32: An atomic value is a basic data value such as a string, number, or boolean, not associated with a node.

Answer-33: XQuery uses declare namespace and namespace prefixes to handle XML namespaces.

Answer-34: The let clause assigns a value to a variable. Example: let $total := sum(/books/book/price).

Answer-35: for iterates over a sequence, while let assigns a single value or sequence to a variable.

Answer-36: XQuery allows custom functions defined using declare function. Example: declare function local:add($a, $b) { $a + $b };.

Answer-37: The return clause specifies what to output for each iteration in a FLWOR expression.

Answer-38: XQuery 3.1 supports JSON data manipulation using JSON-related functions like json-to-xml() and xml-to-json().

Answer-39: A node is a fundamental unit of an XML document, including elements, attributes, text, comments, and processing instructions.

Answer-40: The fn:replace() function replaces parts of a string using a regular expression. Example: replace("123-456", "-", "").

Answer-41: Use the group by clause. Example: for $book in /books/book group by $author := $book/author return $author.

Answer-42: Predicates are conditions enclosed in square brackets used to filter nodes. Example: /books/book[price > 20].

Answer-43: The fn:tokenize() function splits a string into a sequence based on a delimiter or pattern. Example: tokenize("a,b,c", ",").

Answer-44: Use multiple keys in the order by clause. Example: order by $book/author, $book/title.

Answer-45: The default keyword sets a default namespace or collation. Example: declare default element namespace "http://example.com";.

Answer-46: Use XML entity references. Example: <, >, and &.

Answer-47: The text() node test matches text nodes in an XML document. Example: /books/book/text().

Answer-48: Use the validate expression. Example: validate { doc("file.xml") }.

Answer-49: Whitespace in queries is ignored, but whitespace within string values or text nodes is preserved.

Answer-50: The fn:error() function raises an error explicitly. Example: error("Custom error message").